In general, a cluster is provided in front of a driver's seat in a vehicle to display vehicle driving information, information related to operating states of various devices and machines (such as an engine), warning messages, or the like, using characters or figures. The cluster may be provided with a plurality of gauges and indicators. For example, the cluster may be provided with a speedometer for displaying the instantaneous speed of a vehicle, a trip odometer, an integrator, a revolutions per minute (RPM) meter for displaying revolutions of the engine per minute, a fuel gauge for displaying the amount of fuel remaining, a temperature indicator for displaying the temperature of a coolant, as well as a brake warning light, a seat-belt warning light, an anti-lock braking system (ABS) warning light, and various gauges and indicators for displaying the operating states, warning states, and the like of in-vehicle subsystems.
Recent clusters may include a liquid crystal display (LCD) such as a double-layer super twisted nematic (DSTN)-type LCD or a thin film transistor (TFT)-type LCD in order to display various information in the form of graphics, icons, words, numbers, and the like. A conventional apparatus for controlling a display of a cluster displays various icons in three colors, i.e., red, amber, and green, depending on the degree of importance, displays a set speed of a smart cruise control (SCC) system as a solid line on a speedometer, and displays a speed limit of a road acquired by interlocking with a navigation system as two-dimensional (2D) digital numbers. However, since the conventional apparatus for controlling a display of a cluster is limited to displaying information in a 2D manner, the recognition and intuition of a vehicle operator may also be limited.